Abstract:

Aiming at the large energy consumption and low recovery rate of the conventional concentration process for cellulose green solvent N-methylmorpholine-N-oxide(NMMO), this paper proposed a method for concentration and recovery NMMO based on vacuum membrane distillation (VMD). The influences of vacuum degree,  feed-liquid flow rate, feed-liquid temperature and feed-liquid concentration on the VMD process were investigated, and the feasibility of deep concentration and the system operating stability were studied. The results indicated that the membrane distillaation flux increases with the increase of vacuum degree, feed-liquid temperature and feed flow rate, and decreases with the increase of feed-liquid concentration; while the permeate concentration decreases with the increase of  vacuum degree, but has no obvious dependence on feed-liquid temperature, feed-liquid flow rate and feed-liquid concentration. The VMD process can successfully concentrate 100 g/L NMMO into 467.2 g/L, and the system maintains good operating stability in the operation process of 5 concentration preiods totally for 60 h , has the rejection coefficient to NMMO always maintained at above 99.88%. The VMD process has good technical feasibility feasible.

Key words: vacuum menbrane distillation, green solvent, N-methylmorpholine-N-oxide, hollow fiber membrane